Although former Gov. Mitt Romney of Massachusetts is leading former U.S. Sen. Rick Santorum of Pennsylvania in the hunt for delegates, it is next to impossible for Romney to wrap things up before the Texas primary on May 29. And Santorum has led most public opinion polls in conservative Texas, which has the country's second-largest number of delegates at stake, with 155.

Two other factors point toward a competitive Texas race: Gov. Rick Perry's endorsement of former House Speaker Newt Gingrich, whose campaign has been struggling, and Rep. Ron Paul's loyal following in his home state.

"There's going to be presidential campaign activity for the first time, really, since 1976," said Paul Bettencourt, a conservative talk show host and former tax assessor-collector in Harris County. "I think there will be an active race."

On Thursday, Santorum swooped into San Antonio for a town-hall-style meeting, where he promised to mount a vigorous campaign in Texas and told voters that the state could help "reset" a race that many pundits have said is Romney's to lose.

Texas normally holds its primary in March, but a battle over new maps for legislative and congressional districts forced a court-ordered delay this year.

More than a dozen states hold primaries between now and the Texas contest, so it is not clear how competitive the campaign will actually be. But unless Romney's opponents pull out before late May, Texas will probably get more attention from the Republican candidates than it has received since the state began using primaries as part of the delegate selection process.

That first happened in 1976, a year of fierce competition between President Gerald Ford and former Gov. Ronald Reagan of California. Ford was the preferred candidate of the Republican establishment here, and he had piled up far more delegates than Reagan by the time of the May 1 primary.

But Reagan's message of limited government and a more robust national defense struck a chord among voters, and he won Texas in a landslide, picking up every delegate.

Gilbert Garcia, author of Reagan's Comeback: Four Weeks in Texas That Changed American Politics Forever, said Reagan's win put him back into competition in the 1976 race. And though Reagan fell short at the convention in Kansas City, Mo., the Texas victory set the stage for his national triumph four years later, Garcia said.

Although Santorum could tap into the same coalition that Reagan put together 36 years ago, Romney will probably outspend his rivals. And money matters a lot in a state with so many expensive television markets.

A hot race could also significantly increase turnout, as the competition between Reagan and Ford did. That, in turn, could have an impact on the candidates running for the U.S. Senate and the hundreds of others competing in legislative and county contests.

Steve Munisteri, the state Republican Party chairman, said high turnout could also help Republicans expand its voter outreach ahead of November. A contested race could also leave bitterness and division behind, but Munisteri said that is the nature of politics. "I'll take a risk of divisiveness in return for having people get more activated," he said.